Accessing the Erythrocyte Cytoplasm: A Method for Manipulating the Intracellular Environment of Erythrocytes for the Study of Malaria Invasion, Trafficking and Growth.

Invasion of erythrocytes by malaria parasites requires participation of both parasite ligands and host determinants. Further recent studies show that erythrocyte G protein signaling regulates malarial infection. Many of the G_s-associated signaling components reside on the cytoplasmic leaflet of the erythrocyte plasma membrane, rendering them inaccessible to most extracellular probes. Since erythrocytes are enucleated and terminally differentiated, they cannot be transfected to express exogenous transgenes. We have modified methods of hypotonic lysis and isotonic resealing to generate loaded erythrocyte ghosts that can be efficiently infected by Plasmodium falciparum and sustain normal levels of intraerythrocytic parasite growth and replication. Further, we show that these ghosts can be filled with various membrane-impermeable peptides or other proteinaceous cargoes for studying signaling and transport events inside the erythrocyte. Resealed ghosts morphologically resemble normal erythrocytes, albeit with reduced hemoglobin content. Other measures of erythrocyte function and malarial infection are being investigated. Studies will be presented on the use of ‘reconstituted’ erythrocytes in elucidating mechanisms parasite invasion as well as parasite protein trafficking in erythrocytes infected by P. falciparum.